1. Field of the Invention
The present invention relates to information encoding and/or decoding in a mobile communication system, and more particularly, to a method of decoding a received signal efficiently by considering information that is repeatedly transmitted or varies with a long period.
2. Discussion of the Related Art
First of all, contents of basic coding theories necessary for the description of the present invention are explained as follows.
Assuming that a general binary error correction code is represented as [n, k, d], ‘n’ indicates the bit number of coded codeword, ‘k’ indicates the information bit number before coding, and ‘d’ indicates a minimum value among inter-codeword distances. Since the code is binary, a code length of codeword is 2n and the total number of coded codewords becomes 2k.
For convenience, if a minimum distance does not matter considerably, the binary error correction code can be represented as [n, k]. In the following description, unless there is special mention, a value indicated by n, k and d shall be fixed to the above contents. In this case, a code rate R is defined as a value resulting from dividing the information bit number by the bit number. Namely, the code rate R is defined as R=k/n.
In the following description, Hamming distance in coding theory is explained. Hamming distance means the number of non-matched bit values corresponding to each other between binary codes having the same bit number. If Hamming distance d is represented as d=2a+1, it is able to correct errors amounting to the number ‘a’. For instance, if two codewords are ‘101011’ and ‘110010’, Hamming distance between the two codewords is 3.
Meanwhile, a minimum distance means a minimum value of a distance between random two codewords belonging to the code. The minimum distance is one of important estimated quantities indicating a good extent of code. And, the above-mentioned Hamming distance is used as a distance. The minimum distance is widely used as an index for estimating performance o general codes. In particular, as a distance between codewords generated through a coding process gets greater, it becomes less probable that a corresponding codeword is determined as a different codeword. Hence, coding performance becomes better. And, entire code performance is estimated by a distance between codewords having worst performance, i.e., a minimum distance between codewords. Consequently, a good code having a minimum distance maximized shows good performance.
In the next generation mobile communication system, control information is very important in determining performance of system by carrying information of system configuration, transport channel and the like. The control information is configured to have a short length to use system resources as small as possible. The control information is coded by coding scheme strong against channel error and is then transmitted. For instance, in the 3GPP mobile communication system, coding scheme for control information adopts a block code of short length based on RM code, tail-biting convolutional code, repeated code of simplex code or the like.
Meanwhile, the above-mentioned control information can be categorized into information slowly varying with a long period and information for carrying different information at each transport timing point with a short period. In case that both of the informations differing from each other in type need to be simultaneously transported, a receiving side is able to use information in a manner of efficiently decoding a received signal using a fact that specific information is repeated for a prescribed period to carry the same information. Yet, this scheme has not been discussed in detail.